Treatment of metals and chiefly of macnesium and its alloys



F. BADGER Nov. 14, 1933.

TREATMENT OF METALS AND CHIEFLY OF MAGNESIUM AND ITS ALLOYS Filed Nov.30, 1951 Patented Nov. 14, 1933 UNITED STATES TREATMENT OF METALS ANDCHIEFLY OF MAGNESIUM AND ITS ALLOYS Frederick Badger, London, EnglandApplication November 30, 1931, Serial No.

578,139, and in Great Britain December 2,

Claims. (Cl. 7558) mixture of such chlorides, has been added to themixture, but the presence of such substances may contaminate the metal.

I have now found, that the meltingpoint of the mixture of magnesiumfluoride and magnesium chloride will be lowered if instead of using theanhydrous magnesium chloride, a somewhat hydrous magnesium chloride isemployed. Ex-

perience has shown that the presence of this hydrated mixture in thebath produces no prejudical effect, provided the proportion of water ismaintained below a certain limit, and this has led to use as a cleaningand refining flux, no

longer a mixture of magnesium fluoride and anhydrous magnesium chloride,but a mixture of magnesium fluoride and hydrous magnesium chloride.

I have now observed (contrary to what would be expected), that goodresults can be obtained with a mixture of 40% magnesium fluoride and 60%magnesium chloride, this latter being preferably free from oxide andcontaining from 2 to 20% of water. A small percentage of water is quitesufficient for the obtainment of a flux which will melt at the usualrefining tempera- -3 tures (i. e. somewhat above the melting point ofmagnesium, 651 C.). The percentage of water should, however, not beallowed to rise above 20 to 25%, otherwise the refining properties ofthe flux will be damaged.

The invention also embraces a method of forming above magnesium or itsalloys, a solid protective crust preferably consisting of a mixture ofmagnesium fluoride and hydrous magnesium chloride. Thus when the metalis poured, the

' crust will not'be carried along with the metal as often occurs whenthe crust is in the liquid or powdered state, or in pieces.

. The invention further embraces a receptacle adapted to receive themetal to be melted, or

the molten metal, and comprising one or both of the followingarrangements.

1. A cup or the-like which is situated at the upper partof the crucible,or even on the cover, and whose interior communicates with the interiorof the crucible, the said cup or the like betecting it against theeffects ofthe air or the like. i

2. A screen which is mounted on the crucible, or even on its cover, onthe side at which the metal is poured, and which is provided with one ormore relatively narrow passages which allow the metal to flow whileretaining the impurities. 5 The said screen-preferably consists of acomb having several teeth and affording passage to the metal.

In particular, when the metal is melted in a crucible and is transferredto an intermediate ladle prior to pouring into the molds, there is usedin conformity to the present invention a crucible whose pouring orificeis situated on the side of the crucible and below the level of themolten metal in the said crucible, and a closing plug serves to retainthe liquid until the pouring is to take place.

By way of example, the accompanying drawing shows a crucible embodyingthis last-mentioned arrangement. Said drawing shows a vertical sectionof the apparatus, the larger element being the furnace and its crucible,and the smaller element being the ladle, both as described herein.

According to the drawing, about 4" from the top of a cast steel meltingpot 1 there is a projecting lug 2 which is bored out with a tapered 35hole in order to take a closing plug 3.- The pot 1 is placed in atilting furnace 4, heated by any suitable means, which has a slot 5 cutout at'the front to accommodate a projecting lug 2 which should protrudeslightly from the furnace. 1

The pot 1 is then charged with magnesium which is melted and refinedbelow 300 C. with a flux composed of 40% magnesium fluoride and 60% ofhydrous magnesium chloride, special care being taken that the. surfaceof the molten metal is about 2" above the outlet hole of the lug 2.

The metal being thus completely cleaned, thege is projected on thesurface of the metal a mix ture of magnesium fluoride and hydrousmagnesium chloride, thus forming a crust 6 which solidifies.

A small collared pin is inserted into the crust during its formation, soas to provide a hole for the insertion of a pyrometer element. The metalis then ready for transferring to the intermediate ladle 8 prior topouring into the moulds.

The ladle 8 is of cast iron having'a spout 9 and a removable cover 10which is preferably tightfitting.

The top of the ladle has a flanged edge 11 which is machined to a smoothface to take the cover 10. The cover, which is also machined smooth, hasa cast iron cup 12 drilled with small holes 13 by which the interior ofthe cup 12 communicates with the interior of the ladle, and a pivotedremovable cover 14 is fitted on the top of the cup. There is also a hole15 in the cover for filling from the crucible, and this hole can beclosed to advantage by a tight-fitting removable lid 16.

The'cast iron cup is charged with an inert gas or a chemical substancewhich when the ladle 8 is heated or when the metal is poured in, willgive off an inert gas in order to prevent oxidation, the gas passinginto the ladle through the small holes 13 drilled in the cup 12.

The ladle 8 is heated before the metal is poured in, and is then carriedin a pouring ring to the tilting furnace 4; sulphur or any suitablechemical substance is placed in the cup 12 which is immediately coveredin at the top by means of the removable cover 14.

The plug 3 is then removed, the furnace is tilted forward, and themetal, whose temperature has been checked by a pyrometer, is then pouredinto the ladle 8 through the tapered outlet hole of the crucible, whilstthe body of the molten metal is covered and protected by the solid crustand by a stream of sulphurous anhydride (S02) which is passed throughthe pyrometer hole by means of a nozzle. The metal in the ladle, whichis kept perfectly clean by means of the inert gas contained therein, isthen poured into the mould to produce castings free from flux inclusionsor oxidation.

The crucible 1 may contain from 180 to 200 lb.

of metal and the ladle 8 from 25 to 35 lb.

The cover is provided with a comb-shaped deand hydrated magnesiumchloride to the metal to be melted.

2. Amethod as claimed in claim 1, character= ized by the fact that themagnesium chloride contains from 2 to 20% of water.

3. A method as claimed in claim 1,-characterized by the fact that therefining is effected at a temperature below 800 C.

4. A method of protecting molten magnesium and its alloys againstoxidation by the atmos= phere, characterized by the fact that there isformed a ove the molten metal a solid crust of a mixture 0 hydrousmagnesium chloride and magnesium fluoride.

v. 5. A method of refining magnesium and its ailoys wherein the metalwhich is melted and treated with the flux according to claim 1, is thenpoured into a receptacle and preventing oxidation ofsaid metal therein,by the presence of an inert 1105 FREDERICK BADG.

